This invention relates to fluid filters, such as disposable-type oil filters, and methods for manufacturing same.
The type of oil filter currently used for automobile and aircraft engines is the "spin-on," metal, disposable type. This filter is relatively inexpensive to mass produce and relatively easy to install and replace.
A conventional spin-on, disposable-type, fluid filter is shown in FIG. 1 herein and is indicated generally by reference numeral 10. This filter 10 includes: a metal housing 12 having a cylindrical side wall 14; a shaped, closed end 26 having means 70 such as a hex nut for cooperation with a filter wrench (not shown); and an opposite, open end 28. The housing 12 can be made according to the drawing and ironing process described in co-assigned U.S. Pat. No. 4,541,265, issued to Dye et al.
The housing 12 shown in FIG. 1 is particularly suitable for aviation purposes. That is, aviation filters are required by federal regulations to accept an additional wire connection (not shown) between tabs 71 formed on the closed end 26 of the housing 12 and a filter mount 46 to ensure that the filter, even if same loosens during operation, will not come off the filter mount 46.
The filter 10 also includes: a filter element 16 positioned around a perforated center tube 18, bordered by end caps 20, 22, and positioned within the housing 12 by an element guide 24; a thick, metal end plate 30; and a retainer 32. Each of the end plate 30 and retainer 32 includes inlet openings 34 and 36, respectively, to allow oil to flow into the filter 10. The housing 12 and end plate 30/retainer 32 combination are connected at the open end 28 by a known welding process (aviation applications) or clinching process (automotive applications) to create a leakproof seam therebetween.
An annular, resilient sealing gasket 40 is retained in an annular channel 42 formed on the retainer 32. The gasket 40 cooperates with a flat sealing surface 44 on the filter mount 46. The filter mount 46 is formed on an engine 48 and includes oil flow openings 50. Located centrally of the end plate 30 is a threaded aperture 52 which receives a threaded stud 54 carried by the filter mount 46. The threaded stud includes a hollow interior 55.
The filter 10 also includes an antidrain back (ADB) valve 56, an ADB spring 58, a relief valve spring retainer 59, and a pressure relief valve assembly 60. The assembly 60 includes a compression spring 62, a piston support 64 and a piston 66. An example of a conventional pressure relief valve assembly is described in Assignee's U.S. Pat. No. 4,497,706.
In order to install this filter 10 on the engine 48, the filter 10 is spun clockwise onto the stud 54 via the threaded aperture 52. To remove same, a filter wrench is engaged with the means 70 and turned counterclockwise.
During normal operation, flow of oil is from the engine 48, through the oil flow openings 50 formed in filter mount 46, into the inlet openings 36, 34 formed in the retainer 32 and end plate 30, respectively, against and around the ADB valve 56 with some turbulence as noted by arrows A, through the filter media 16, through the center tube 18, through the central aperture 52, into the hollow interior 55 of the stud 54 and back to the engine 48. In the "bypass" mode, when oil pressure at the pressure relief valve assembly 60 exceeds a predetermined level, oil flows through the assembly 60 and directly into the center tube 18, thereby bypassing the filter element 16 and returning to the engine 48.
The common and continuing problems of this conventional metal, spin-on, disposable filter are discussed below.
First, due to the great pressures encountered during operation, it has been thought necessary to manufacture the area of attachment of the filter 10 to the filter mount 46, particularly the end plate 30, from a metal whose thickness and strength can withstand these pressures. Of course, a filter design requiring thick, strong metal for the area of attachment results in high raw material and manufacturing costs.
Second, the total raw material cost of the filtration process components, i.e. filter element 16, related adhesives, etc., is less than a third of the total raw material cost of each filter 10. The remaining two-thirds of the cost is related to the non-filtration process components, i.e. the sealing gasket 40, end plate 30, etc. Due to this disproportional cost ratio, it is highly desired to minimize the cost of the non-filtration process components.
Third, the conventional fluid filter 10 requires machining or cutting of various parts, such as the threaded stud 54 and central aperture 52. The goal of generating high volume production of fluid filters including quality threads, without leaving traces of chips and burrs, has posed serious, longstanding problems in the industry.
Fourth, the inlet openings 34 have axes which are substantially parallel to the longitudinal axis of the filter 10. Such openings 34, in combination with the ADB valve 56 and ADB spring 58, cause the oil flow in such a manner as to create high non-laminar flows and high initial pressure restrictions.
Fifth, the end plate 30/retainer 32 combination must be assembled through an intricate clinching or welding process, adding cost to the production.
Accordingly, the fluid filter described above necessarily demands that relatively thick metal be used in the area of attachment, is relatively expensive and difficult to manufacture, and frustrates laminar fluid flow.
Assignee's U.S. Pat. No. 4,764,275, issued Aug. 16, 1988 and entitled "Fluid Filter And Method For Attaching Same In Sealing Relation To A Filter Mount," which is incorporated by reference herein, proposes a more easily installed and removed fluid filter, wherein the filter and filter mount incorporate interlocking means. The interlocking means includes, e.g. pairs of corresponding flanges formed on the filter and filter mount, respectively. However, the fluid filter described therein still does not fully overcome the drawbacks of known fluid filters.
First, if an adaptor is used to retrofit a conventional filter mount to receive the filter described in the co-pending application, the adapter must still be machined resulting in a costlier part.
Second, the filter housing must have formed therein, in the area of the interlocking means, an area for properly containing a sealing ring to seal against the filter mount. Forming this sealing ring retainer is difficult and labor intensive.
Third, the seal is not an "off the shelf" common seal, but rather a more expensive "quad" seal.
Fourth, interlocking means in the form of flanges must be roll formed or machined and must be positioned and then welded to the metal housing, all of which are labor intensive steps.
Fifth, there are still a relatively large number of components in this filter, thus increasing manufacturing steps and costs.
Sixth, the pressure relief valve assembly and ADB valve components are machined out of metal and are intricate to assemble.
Thus, it can be seen that the Assignee's earlier invention, if manufactured in metal, presents problems in both the component manufacture and assembly operations.
Neither of the above-described fluid filters have the novel features of the invention disclosed herein which overcome these disadvantages.